import matplotlib.pyplot as plt
import numpy as np 

x = np.linspace(0, 100, 1) 
y1 = np.sqrt(np.power(x, 2) + np.power(400, 2))
plt.figure(num=3, figsize=(8, 5)) 
plt.plot(x, y1) 
plt.xlim((0, 100)) 
plt.ylim((300, 500)) 
plt.xlabel('x axis') 
plt.ylabel('y axis') 
# my_x_ticks = np.arange(-5, 5, 1.5) 
# my_y_ticks = np.arange(-2, 2, 1.5) 
# plt.xticks(my_x_ticks) 
# plt.yticks(my_y_ticks) 
plt.show() 

